PROBLEM TO BE SOLVED: To provide an airway adaptor to which a respiration gas detection sensor can be detachably attached with force as small as possible.SOLUTION: An airway adaptor 10 comprises an airway casing 11, a fitting part 21, and a projection. The airway casing 11 comprises a passage 12 formed therein allowing respiration gas of a living body to pass through. The fitting part 21 is formed in the airway casing 11 and can be detachably fitted to a sensor. The projection is disposed in the fitting part 21 and comprises a contact part 24a and a noncontact part 24b. When the airway adaptor 10 is mounted on the sensor, the contact part 24a is brought into contact with the sensor and the noncontact part 24b faces the sensor so as to be separated from the sensor.
